This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Anthropogenic environmental toxins, even at low doses, cause some measure of biological change to take place, within plants, animals, microbes, or even humans. The goal of the UC Davis Superfund Program is to discover ways to observe and quantify these biomarkers of environmental impacts, so that the sources and causes of these impacts can be understood, assessed, traced, and remediated. To that end, the Program includes AMS quantitation as one of its competencies in its analytical core. This analytical core serves several of the Program projects, including Soil and Waste Transport, development of Immunochemical Biomarkers, Pulmonary Biomarkers, and Reproductive Biomarkers. Accelerator mass spectrometry (AMS) plays an important role in the assessment of human exposure to toxic substances and in probing the mechanistic basis of toxicity in humans and in other host species. It is a core technology in our program of using biomarkers of environmental exposures to toxic substances from agricultural and industrial activities. We define urinary, pulmonary, reproductive, and circulating biomarkers of specific toxic exposures that are quantifiable using assays such as immunoassays, protein mass spectrometry, chromatography, and direct quantitation of isotope labeled toxins with AMS. AMS also provides calibration of the other assays through correlation of isotope label incorporation from toxins into a host. Quantitation of a derived biomarker is then calibrated by the uptake of toxin indicated by the AMS measurements. In the case of Transport, the investigators are assessing the biological activity of the recently used fuel additive, methyl-tert-butyl-ether (MTBE), which leaked into the ground from fuel depots over the past decade. The binding of 14C-MTBE to mammalian protein is being studied to determine if the compound presents a threat to cellular systems. These laboratory studies are freely done with the levels of 14C needed to interact with cell cultures, but much of the Program is concerned with quantifying biomarkers in natural settings where radiotracer release is not possible. The preferred technology for quantifying recognizable biomarkers is the immunoassay which can eventually be made into field-usable kits. It is important to choose the right target for immunoassay development, such as the most likely metabolite or hormonal response of a chemical exposure. AMS is a particularly valuable technology for the discovery of optimal immunoassay targets because it reveals all metabolites of an isotope-labeled xenobiotic, even at low dose exposures. We found that the di-dealkyl mercapturate metabolites of atrazine were the most prominent lasting biomarkers of this ubiquitous herbicide in humans. Immunoassays are developed for these biomarkers. There are "marker" species in ecosystems which are sensitive to environmental change, much like the canaries of past centuries in coal mines. An increasing number of polutants are being seen as hormonal mimics that act as "poison" to a species by imparing its reproductive success. We are using small quail as one such example and are finding the metabolites of testosterone or cortisone in their fecal droppings, which are used as sample so as to avoid stress effects in a captured bird. The pattern of metabolites will be quantified to find which might be signs of slowly developing environmental stresses. The birds are small, and cannot be heavily dosed, so the sensitivity of AMS is needed. Pulmonary responses to environmental chemicals need to be studied from respiration of environmentally relevant doses. The dose deposition in specific proteins of lung tissue of model animals is poorly quantified by present methods that provide a large exposure followed by protein separation on two dimensional gels followed by long term (1 month) autoradiography. AMS has the sensitivity for appropriate doses and sequential gel separations have been worked out to maximize target protein discovery. The AMS core serves to identify prominent biomarkers of exposure for fieldable assay development and quantifies exposures to labeled compounds for the Program researchers.